Pulmonary Hypertension in Chronic Lung Diseases: What Role Do Radiologists Play?

Abstract

Pulmonary hypertension (PH) is a pathophysiological disorder, defined by a mean pulmonary arterial pressure (mPAP) > 20 mmHg at rest, as assessed by right heart catheterization (RHC). PH is not a specific disease, as it may be observed in multiple clinical conditions and may complicate a variety of thoracic diseases. Conditions associated with the risk of developing PH are categorized into five different groups, according to similar clinical presentations, pathological findings, hemodynamic characteristics, and treatment strategy. Most chronic lung diseases that may be complicated by PH belong to group 3 (interstitial lung diseases, chronic obstructive pulmonary disease, combined pulmonary fibrosis, and emphysema) and are associated with the lowest overall survival among all groups. However, some of the chronic pulmonary diseases may develop PH with unclear/multifactorial mechanisms and are included in group 5 PH (sarcoidosis, pulmonary Langerhans’ cell histiocytosis, and neurofibromatosis type 1). This paper focuses on PH associated with chronic lung diseases, in which radiological imaging—particularly computed tomography (CT)—plays a crucial role in diagnosis and classification. Radiologists should become familiar with the hemodynamical, physiological, and radiological aspects of PH and chronic lung diseases in patients at risk of developing PH, whose prognosis and treatment depend on the underlying disease.

Sarcoidosis-Associated Pulmonary Hypertension

“…Multimodal imaging techniques in SAPH include chest X-ray, CT scan, ventilation/perfusion (V/Q) scanning, CMR and other innovative techniques [64].…”

“…A prospective evaluation of a large cohort of patients (n = 246) showed no difference on CT scan between patients with or without PH in terms of lymph node enlargement, parenchymal involvement and thickening of bronchovascular bundles [11]. In contrast to parenchymal abnormalities, some vascular images are good indicators of PH, such as a pulmonary artery diameter > 29 mm, a right ventricle (RV)-to-left ventricle (LV) ratio > 1, or a pulmonary artery (PA)/ascending aorta (AA) > 1 [53,64,65], with a 65% sensitivity and a 83% specificity for the latter [66]. The ratio of PA diameter to BSA is even more predictive [67].…”

“…Given the well-known risk of VTE episodes and of CTEPH in sarcoidosis [40,69,70], a systematic search for the latter should be performed in sarcoid patients with a suspected PH. Pulmonary angiography will help to reach this diagnosis, but dual-energy CT (DECT) [64,71,72] provides more information, including morphological information on the vasculature and functional information on perfusion. Primarily used to replace V/Q scanning, which does not allow any evaluation of the lung parenchyma nor mediastinal lymph nodes, it has also been investigated as a screening tool for pulmonary hypertension whatever its cause [73].…”